package 实验0701;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
interface  IntegerStack{
	public Integer push(Integer item);
	public Integer pop();
	public Integer peek();
	public boolean empty();
	public int size();
}

class ArrayListIntegerStack implements IntegerStack{
	private List<Integer>list;
	public ArrayListIntegerStack(){
		list = new ArrayList<Integer>();
	}
	@Override
	public Integer push(Integer item) {
		if(item == null)
			return null;
		list.add(item);
		return item;
	}
	@Override
	public Integer pop() {

		if(list.size()==0)
			return null;
		return list.remove(list.size()-1);
	}
	@Override
	public Integer peek() {
		if(list.size()==0)
			return null;
		return list.get(list.size()-1);
	}
	@Override
	public boolean empty() {
		return list.size()==0?true:false;
	}
	@Override
	public int size() {
		return list.size();
	}
	
	public String toString(){
		return list.toString();
	}
	
	
}
public class Main {
	public static void main(String[] args) {
		 
 
		Scanner in = new Scanner(System.in);
		ArrayListIntegerStack arr=new ArrayListIntegerStack();
		int m = in.nextInt();
		for(int i=0;i<m;i++)
		{
		Integer a =	arr.push(in.nextInt());
		System.out.println(a);
		}System.out.println(arr.peek()+","+arr.empty()+","+arr.size());
		System.out.println(arr);
		int x =in.nextInt();
	    for(int i=0;i<x;i++)
		{
		
		System.out.println(arr.pop());
		}
	    System.out.println(arr.peek()+","+arr.empty()+","+arr.size());
		System.out.println(arr);
	}
}
